The invention relates to the field of paging systems utilizing battery powered portable pagers.
Paging systems have used various methods for reducing the power consumption of battery-operated portable pagers in order to miniaturize the pager unit. One such approach involves supplying power to the receiver circuitry only during predetermined time slots in which data relating to the particular pager unit is broadcast. In the absence of accurate synchronization between the transmitter and receiver, a long time slot is required to insure that the pertinent data is received and thus more power is consumed.
Apart from paging systems there are methods by which a clock can be remotely reset by a transmitted signal. Tohyama et al., U.S. Pat. No. 4,358,836, for example, shows a method for setting a watch from a transmitted time announcement signal.
A combination of a pager utilizing time slot transmission with a resettable watch is shown by Natori et al., U.S. Pat. No. 3,937,004. The Natori system shows a watch controlled by a counter which is periodically reset by a transmitted signal. The use of an internal counter allows errors to accumulate since the counter will have some amount of error, and the error in each count will be added to the time indication. Thus, the watch may stray from the correct time. This straying requires the use of a large time slot to accommodate errors in the time when the pager's receiver is powered up.